Forces loyal to Libya's parallel government on Tuesday threatened to bomb oil tankers approaching the Libyan coast without permission from authorities in the country's east.
Rival government threatens oil tankers
The Tobruk parliament has refused to hold a vote of confidence in the GNA, formed as the result of a UN-backed accord in December.
"We cannot allow Libyan oil to be exported except via the National Oil Company in Benghazi," said General Abdulrazzaq al-Nadhouri, chief of staff for forces loyal to the rival government based in the eastern city of Tobruk.
"We will target any boat that approaches the Libyan coast without prior agreement with the NOC in Benghazi," he told AFP.
Oil is Libya's main natural resource with reserves estimated at 48 billion barrels, the largest in Africa. But production was hit hard in the wake of the 2011 revolt that ousted dictator Moamer Kadhafi.
Like many state institutions, the country's oil company was split into two as rival governments emerged.
Nadhouri's threat came as the UN-backed Government of National Accord (GNA) based in the capital Tripoli attempts to revive Libya's all-important oil sector.
His comments are a blow to hopes that the sector would be strengthened by an agreement early this month between rival leaders of the NOC to unify their ranks.
He said his threat was a response to an agreement between UN envoy Martin Kobler and Ibrahim al-Jadhran, the leader of militia set up to guard the country's main oil facilities, to reopen the key Ras Lanuf and Al-Sidra export terminals.
Jadhran's militia backs the GNA and has joined GNA-allied forces fighting the Islamic State group in Sirte, 450 kilometres (280 miles) east of Tripoli.
The terminals were closed after an attack by IS early this year.
In a statement released on Tuesday, the NOC in Tripoli said the Libyan oil and gas sector "should be kept aside from political conflicts".
It said NOC officials had met representatives of international oil companies including Italy's ENI and France's Total in Vienna between Thursday and Sunday.
Those present agreed on "the urgent need to end the closure of the oilfields and terminals without any conditions", the NOC statement said.
Libya's oil production has dropped from 1.5 million barrels per day (bpd) to around 300,000 bpd since the fall of Kadhafi.
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